Method of bonding steel to silver



Patented Jan. 1, 1952 Serial No. 605,8

3 Claims. 3

This invention relates to improvements in lam inated bearings and in particular to steel-backed bearings wherein a layer of silver is attached to a steel backing, the silver layer being used as the bearing surface. According to present practice in the silver-clad bearing industry, serious difilculties are encountered in securing a good bond between the silver layer and its steel backing.

According to my invention this difilculty is overcome by applying and fusing a layer of .fine ly divided spaced particles of nickel to the steel surface onto which it is desired to attach the overlay of silver. According to my invention nickel powder is applied to the steel backing either by brushing it on dry or by spraying it on with metalizing apparatus. After the nickel powder has been applied to the steel surface areas to which it is desired to attach the silver, according to my invention I subject the steel part having the application of nickel particles thereon to heat in an inert atmosphere at a temperature sufiicient to fuse the nickel particles to thesteel. It is preferable that the nickel when fused does not form a continuous sheathing of nickel where applied. In other words it is desirable that the nickel be so thinly applied that when fused the resulting coating is somewhat porous and dispersed so that it does not completely coat the steel, but forms an extremely thin lattice work over the areas to which it is desired to attach the silver overlay.

An alternate method of securing the attachment of finely divided nickel particles to the steel backing material is to flash-plate the steel backing material in a nickel solution and then subject same to heat in a nonoxidizing or a reducing atmosphere, to cause the nickel particles so electrodeposited to fuse to the steel base material. This electrodeposition method has the objection that foreign material which is undesirable may be deposited on the steel in addition to the pure nickel particles which it is desired to have deposited and fused.

Another method of applying nickel particles to the steel is to apply a very thin layer with a binder as of vinyl resin and naphtha and fine nickel powder which does not leave any appreciable ash in the layer so applied. This applied thin layer is also subsequently subjected to heat in order to fuse the nickel particles to the steel. In any case the thinnest obtainable layer of nickel is most desirable. The heat should be such that an alloying effect is secured between the nickel and the steel so that after heat treatment the nickel cannot be mechanically separated from the steel. The purpose in fusing the nickel particles to the steel backing material prior to the application of the silver is to prevent particles of nickel from floating or dispersing themselves into the silver bearing layer when the silver is molten. For this reason the nickel particles should be firmly anchored to the steel prior to melting the silver. After the heat treatment or firing in of the nickel dispersion. I preferably apply a. layer of pure silver to the nickeled steel surface in a die and press so constructed that-the silver layer will be in intimate contact all over the areas to which it is desired to apply silver. This is done by means of tools and dies and methods .which are known to those skilled in the art of forming sheet metal. It is particularly desirable, in applying the silver shell to the steel backing material, that no space be left around the edges of the silver or between the adjacent silver and steel surfaces so that the silver layer adheres firmly to the steel backing and fits tightly thereto.

The next step, according to my invention, is described in my copending applications, Serial Number 566,172, filed December 1, 1944, now Patent No. 2,510,546, and Serial Number 555,458, filed September 23, 1944, now Patent No. 2,517,762, and is to apply a retaining body to the above assembly of steel and silver preferably of an enclosing briquet of powdered material such as graphite. This enclosing briquet may be applied in a hydraulic briquetting press. The material of the briquet should be such that it will not react deleteriously with the components of the steelnickel-silver assembly when subjected to heat sumcient to melt silver. It is also essential that the mechanical fastening of the sheet silver to the steel backing member be such that none of the briquetting material will creep in between the sheet silver and steel-backing material, because this would interfere with securing good bond between the silver and the steel backing material. After the above assembly has been enclosed in the briquetting material, the briquet containing that assembly is subjected to heat preferably in a high frequency field for a time and at a temperature suificient to melt the silver and cause fusion of the silver to the steel backing having the lattice work of nickel therebetween. The briquet containing the silver and steel assembly may be spun while subjected to heat in a high frequency field in order to secure the assistance of centrifugal force in forcing molten silver to adhere to the surface of the heated nickel latticed steel part.

as an alternate to the use of a briquet in sum porting the molten silver during fusion to the steel backing material, it is possible to enclose the sheet silver portion and the nickel latticed stfeel portion of the bearing in close relationship in a ceramic or quartz die and subject this assembly to heat to cause the silver to fuse to the nickel latticed steel and at the same time support the molten silver so that it will not run out of place or become distorted excessively;

Having thus described my invention, what I claim is:

1. The method of bonding steel and silver comprising sparsely depositing fine nickel particles onto portions of the steel, heating the steel to cause fusion of the nickel particles thereto to form an extremely thin nickel lattice over the steel exposing the steel at the interstices in the lattice, and then applying a silver overlay over such lattice which is bonded to and impregnates such lattice.

2. The method of bonding steel and silver comprising sparsely depositing fine nickel particles ontoportions of the steel, heating the steel to cause fusion of the nickel particles thereto to form an extremely thin nickel lattice over the steel exposing the steel at the interstices in the lattice, and .then applying a silver overlay over such lat- -tice. supporting these components in a heat resis-ting retaining mold, and subjecting these components while thus supported to temperatures sumcient to cause thesilver to directly bond to the steel portion and to impregnate the nickel lattice.

3. The method of bonding steel and silver comprising sparsely depositing fine nickel particles dispersed in a. low ash content binder onto portions of the steel, heating the steel .to cause fusion of the nickel particles thereto to form an extremely thin nickel lattice over the steel exposing the steel at the interstices in the lattice and to cause burning away of the binder, and then applying a silver overlay over such lattice which is bonded to and impregnates such lattice.

, JOSEPH B. BRENNAN.

REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PATENTS Number Name Date 2,024,150 Davignon Dec. 17, 1935 2,190,237 Koehring Feb. 13, 1940 2,198,240 Boegehold Apr. 23, 1940 2,251,410 Koehring et al. Aug. 5, 1941 2,341,739 011: Feb. 15, 1944 2,359,361 Gleszer Oct. 3, 1944 2,364,713 Hensel Dec. 12, 1944 2,386,951 Howe Oct. 16, 1945 2,390,160 Marvin Dec. 4, 1945 2,390,452 Mudge Dec. 4, 1945 2,392,917 Guinee Jan. 15, 1948 

1. THE METHOD OF BONDING STEEL AND SILVER COMPRISING SPARSELY DEPOSITING FINE NICKEL PARTICLES ONTO PORTIONS OF THE STEEL, HEATING THE STEEL TO CAUSE FUSION OF THE NICKEL PARTICLES THERETO TO FORM AN EXTREMELY THIN NICKEL LATTICE OVER THE STEEL EXPOSING THE STEEL AT THE INTERSTICES IN THE LATTICE, AND THEN APPLYING A SILVER OVERLAY OVER SUCH LATTICE WHICH IS BONDED TO AND IMPREGNATES SUCH LATTICE. 